So you're saying Kemp is taller than Barnett then? Maybe he is, but I don't see it. As for DeMarre Carroll, NBADraft.net had him listed at 6'7 and 3/4 or rounding up, that's 6'8. I know that colleges lie about heights, but Kemp doesn't appear that athletic to me either.
http://www.nbadraft.net/2009-nba-draft-combine-player-measurements